1. Field of the Invention
The present invention relates to a roundness measurement device and a method for controlling the roundness measurement device. Specifically, the present invention relates to a roundness measurement device capable of automatically changing an angle position of a stylus, and to a method for controlling the roundness measurement device.
2. Description of Related Art
A roundness measurement device is a known example of a measuring device measuring roundness of a measured object. The roundness measurement device includes a base, a rotation table on which a measured object is placed and which is rotatably provided on the base, a rotational driving mechanism driving the rotation table, a column standing upright on the base, a lifting slider provided to be capable of rising and lowering in a vertical direction along the column, a slide arm provided to the lifting slider so as to be capable of sliding toward a direction orthogonal to a vertical axis, and a detection device that outputs, as an electric signal, a displacement of a stylus which is attached to a forefront end of the slide arm and contacts the measured object.
In the conventional roundness measurement device, when measuring outer/inner circumferential surfaces, a stylus has been supported inclined with respect to a detecting device main body, such that the detecting device main body does not interfere with a work piece (for example, see Japanese Patent Laid-open Publication No. H05-133701). When measuring an inner circumferential surface, especially when measuring an inner circumferential surface of a small diameter hole, a stylus or a detecting device main body interferes with an edge of the hole when the stylus is inclined. Therefore, when measuring the inner circumferential surface, the stylus has been introduced into the hole of the measured object after orienting the stylus vertically.
However, a task of switching the stylus between an inclined state and a vertical state has been conventionally carried out manually by an operator, and thus working performance could not be improved. For example, among a series of measuring operations with respect to the work piece, in a case including measurements of both the outer circumferential surface in which the stylus is inclined and the inner circumferential surface of a small hole in which the stylus is vertical, manual labor to switch the inclination in the middle of operation is required. Therefore, even though a series of measuring operations is automatically carried out, a process was required to stop the automatic operation in the middle of operation and wait for the manipulation by the operator, thus preventing total automation and work efficiency. Furthermore, the stylus can be connected to the motor and the inclination of the stylus can be changed by driving the motor, for example. However, in such a case, the configuration becomes complicated and heat generation of the motor becomes an issue. Thermal expansion caused by the heat generation of the motor may cause a measurement error.